Cranes



Ju 0, 1967 K. F. T. ADOLFSSON CRANES Filed Nov.

United States Patent 3,326,391 CRANES Karl Fritjof Torbjiirn Adolfsson, Bjorns Tradgardsgrand 3, Stockholm, Sweden Filed Nov. 4, 1965, Ser. No. 506,294 Claims priority, application Sweden, July 16, 1965,

5 Claims. (Cl. 212-55) This invention relates to portable load handling swinging cranes of relatively small sizes whch are particularly useful for lifting, handling and positioning moderate loads within relatively narrow ranges, especially but not exclusively in workshops and storages, at building sites, on trucks and the like and more particularly the invention is concerned with improvements in so called rotary cranes including a revolving post and a hydraulically operated, vertically swingable jib having a fixed load carrying device, such as a hook, at its outer end.

It is an object of this invention to provide an improved crane of the type referred to, which makes it possible to move the lifted load not only in substantially fixed circles but also in radial direction relatively to the vertical swinging axis of the crane post and to position the load with a very high accuracy, which all considerably improves the usefulness of the crane.

It is also an object of the invention to provide a crane with the abovementioned features which is safe in use and in which the risk of unintentional and uncontrolled movements of the handled load is substantially eliminated.

A still further object of the invention is to provide a crane of the type referred to which is collapsible into a very compact unit, when not in use, and which is, consequently, requiring a minimum of storage space and, in addition, handy and easy to carry by hand between different locations, if so desired. If the same crane is to be used alternatively in two or more places there will only be needed a special socket in each place as will appear from the following.

In most cases the crane according to the invention is equipped with a hand-operated pump supplying pressure oil to the hydraulic cylinder and piston unit actuating the jib but there is nothing to prevent the use of a motordriven oil pump, if the crane is to be used in places, where electricity or any other source of suitable power is available. Preferably the crane also contains its own oil reservoir. On the other hand, if the crane is to be used in places, such as on trucks, where a supply system for hydraulic oil under pressure is already available, its jack cylinder may, of course, be connected to such system by any suitable, known conduit means permitting the desired swinging movements of the crane.

In its preferred form the hydraulic system of thecrane should also be so designed as to permit manual raising of the jib without using the pump, because this will facilitate the preparation of the crane for work and shorten the time needed for lifting the load to suspended and movable position. Furthermore, the hydraulic system must, of course, include a selective type of oil returning valve for the jack cylinder, which may be handor foot-operated to permit lowering of the jib in an accurately controllable manner.

As an additional feature a load handling rotary crane according to the invention has an extensible jib comprising two main parts which are telescopically movable relative to each other and of which the one or first part is hingedly connected both to the crane post and to the piston of the hydraulic jack unit while the other or second part of the jib forms a longitudinally displaceable but unrotatable extension of the first part and has the load carrying device, e.g. a hook, attached to its outer, free end.

Patented June 20, 1967 'ice In accordance with the present invention a crane of the kind thus defined is mainly characterized by the fact that said second part of the jib is connected to said first part thereof by means of a screw member extending longitudinally through said first jib part and into the inner end of said second jib part, said screw member being rotatably jour'nalled in said first jib part in a manner to prevent it from axial movement in relation thereto and engaging with cooperating threads of said second jib part to move the latter in a controlled manner relative to said first jib part, when being rotated, the end of said screw member remote from said second jib part forming a coupling member to which a screw turning tool can be connected.

Further objects and features of the invention will be come apparent from the following detailed description of an embodiment of the invention which has been illustrated in theaccompanying drawing to which reference will now be had. In the drawing:

FIG. 1 is a side view, partly in section, of a load handling crane embodying the invention, the jib of the crane being in an operative position and partly extended,

FIG. 2 is a side view of the same crane as in FIG. 1 but showing the jib thereof in a contracted and folded down, inoperative positiona part of the crane post Wall being broken away to also show the position of the jackand the whole crane structure being shown removed from its foundation socket so that it may easily be carried away to another place of use, and

FIG. 3 is a front view of the crane as seen from the right in FIG. 2.

The crane thus illustrated in the drawing generally comprises five main components, viz. a crane post 1, a jib 2, a jib actuating jack 3, a foundation socket 4 and a separate lever or crank tool 5.

The crane post 1 is of substantially U-shaped cross section having a closed back and an open front. At its lower end it has a foot portion 1', in which there is secured a downwardly projecting swivel pin 6, which is adapted to enter the foundation socket 4 and be rotatably retained therein in any suitable manner, such as by a removable locking member 7 in FIG. 1 so that the crane may be separated from the socket and carried away, if so desired. The swivel pin receiving socket 4 is in turn intended to be rigidly secured to or in any suitable foundation or crane supporting structure as indicated by dash-and-dot lines at 8 in FIG. 1 and it should be understood that such foundation or supporting structure can be a floor, a trucks platform, a wheeled stand, a concrete body or any other body or structure while is capable to take up the thrust and tilting moment exerted by the crane.

One and the same crane may be alternatively used in several places and with different foundations or supporting structures provided that a matching swivel pin receiving socket 4 has been previously secured in each place and this has proved to be very advantageous both from an economical and a practical point of view, since it considerably decreases the necessary investments and increases the possibilities to utilize each crane intensively and for many different purposes. On the other hand, this means that the crane must be portable and relatively easy to move between those different locations and the crane here shown and described is particularly designed and constructed to meet this requirement, as will appear from the following. Furthermore the crane post 1 is preferably provided with external carrying handles 9 on its side walls.

The jib 2 is hingedly connected to the upper end of the crane post 1 by means of a transverse swing bolt 10 which is horizontal when the crane post is erected and which passes through two lugs or cars 11 secured to opposite sides of the inner end of the jib and straddling the top portion of the crane post. These lugs or ears 11 project laterally from the jib structure in such a manner that the inner end of the jib will occupy an elevated free position over the top of the crane post 1, when the jib is raised for operation substantially as shown in FIG. 1, While at the same time the entire jib structure will come to substantially parallel and extended closely .along the open front of the crane post 1, when the jib is in its folded down, inoperative position as shown in FIG. 2.

Structurally the jib 2 is composed of two telescopically movable parts, viz. a first or main part 12 and a second or extension part 13, both of which are hollow and of substantially rectangular. cross section. The first jib part 12 is the one which is swingably connected to the crane post 1 by means of the lugs or ears 11 above referred to and this part has an open outer end receiving the inner end portion of the second jib part 13 in a manner to permit well guided longitudinal movements of the latter. Since the two jib parts are both of rectangular cross sec tion they are prevented from relative rotation about their common longitudinal axis. The outer, free end 13 of the second jib part 13 is formed as a fork in which a load carrying hook 14 is swingably mounted by means of a bolt 15. Preferably the hook 14 is of the conventional swivel type.

In the inner or rear end of the first jib part 12 there is provided an end wall 16 having a hole in which the rear end portion of a screw member 17 is rotatably mounted in a manner to prevent axial movements. In the illustrated form of the crane this is accomplished by means of simple thrust washers 18 secured to the screw member 17 on opposite sides of the perforated end wall 16, but if so desired other forms of thrust bearings may, of course, be used. The screw member 17 extends longitudinally through the first jib part 12 and engages a nut-like insert 19 secured in the inner or rear end of the second jib part 13, so that rotation of the screw member will cause said second jib part 13 to move longitudinally relatively to the first jib part 12 in an accurately controlled manner. At its forward end the screw member 17 has an abutment or stop 20 preventing the screw member from disengaging the internally threaded insert 19 and also defining the outermost position of the slidable jib extension.

The thread pitch of the screw member 17 and hence of the insert 19 should be also selected that the threads are self-braking whereby unintentional relative movements of the two jib parts 12 and 13 are effectively prevented, and the screw member must, of course, be dimensioned to withstand the stresses to which it may become subjected. The rear end 21 of the screw member 17 projects outside the end wall 16 of the first jib part 12 and is formed to be received in a wrench socket of a separate cranking tool by means of which the screw member 17 may be rotated. This tool will be more closely described in the following. As will be readily understood, the screw actuation of the extensible jib makes it possible to adjust the length of the jib also when a load is suspended in the hook 14 which considerably increases the usefulness of the crane for accurate load positioning tasks.

The vertical position of the outer, free end of the jib 2 is controlled by the hydraulic jack assembly 3 which includes a hydraulic cylinder 22 with a piston 23, a handoperated oil pump 24, an oil return valve 25 and an oil reservoir (not shown). The lower end of the cylinder 22 is swingably mounted inside the hollow crane post 1 by means of a transverse bolt 26 and the upper end of the piston 23 is hingedly connected to a bolt 27 secured between a pair of additional cars 28 projecting from the lower side of the first jib part 13 substantially midway between the ends thereof. The pump 24 is mounted directly on the front side of the cylinder 22 and so is the valve 25, and the oil reservoir is preferably formed between the cylinder 22 and a square casing surrounding the same (not shown) so that the entire hydraulic jack assembly 3 may be easily removed as a unit if repair or replacement should be needed.

The oil pump 24 is so constructed that it may be operated from either side of the crane by means of the same tool 5 as is used for rotating the screw member 17 referred to hereinbefore and for this purpose the pump is formed with an actuating stub 29 on both sides which fits the Wrench sockets of the tool 5 so that said tool may be used as a pump lever as indicated in dash-and-dot lines in FIG. 1. The tool 5 itself comprises a rod 30 having a handle knob 31 at its one end, a first socket 32 substantially in the middle of its length and a second socket 33 at its other end. The two sockets 32 and 33 open in opposite directions and the rod 36 is bent slightly offset between them, so that either socket may be used for connecting the tool to the end 21 of the screw member 17 or to the convenient stub 29 of the pump 24 without the risk of any interference between the tool and the crane structure when the tool is rotated or reciprocated as a pump lever. Obviously, the socket 32 is used when only a moderate moment is required.

The oil return valve 25 is a selective type of valve which permits a fully controlled lowering of the jib 2 and which remains closed as long as the valve actuating member 34 is not actuated by the crane operators hand or foot. The actuating member 34 may be shaped to also retain the contracted jib in folded down position as shown in FIG. 2.

As will be readily understood from the foregoing description, the crane is used with the jib in more or less elevated position. The load to be handled is attached to the hook 14, when the free end of the jib points slightly downwards and when the jib has been sufiiciently extended to place the hook above the load. Lifting is then effected by operating the pump 24 so that the jib is elevated. When the load is freely suspended the whole crane may be rotated until the jib points towards the place where the load is to be positioned and the screw member 17 is rotated to adjust the length of the jib so that the load will be delivered with great accuracy just on the desired spot, when the jib is finally lowered again as a result of an actuation of the oil return valve 25.

When not in use, the crane may be folded together into a very compact and easily portable unit as shown in FIGS. 2 and 3. In this condition of the crane the hydraulic jack assembly 3 is almost entirely hidden within the hollow crane post 1 and the contracted jib 2 substantially covers the open front thereof. When the crane is to be used again, the jib is simply unlocked and swung up by hand into a sufficiently elevated position, which is made possible by the fact that the hydraulic system includes a pump by pass check valve of the well-known type which permits free oil passage to but not from the cylinder.

I claim:

1. In a small size crane comprising a rotary crane post, a vertically swingable, extensible jib mounted on the crane post, and hydraulic jack means to effect vertical swinging movement of the jib; said extensible jib consisting of a first jib part and a second jib part telescopically movable relative to said first jib part and having a fixed load attachment device at its outer free end, hinge means laterally outside said first jib part connecting the end of the latter remote from said second jib part to the top of said crane post so that said end of the first jib part remains fully exposed in all positions of the jib, said telescopically movable first and second jib parts being interconnected by a screw member extending longitudinally through said first jib part and into said second jib part, means rotatably journalling said screw member in said first jib part to prevent relative axial movement thereof, means fixed in said second jib part defining cooperating threads engaging said screw member to move said second jib part in a controlled manner relative to said first jib part upon rotation of said screwmember, an end of said screw member remote from said second jib part projecting from said exposed end of the first jib part and constituting a coupling member which is readily accessible for turning by a screwtu'rning tool, said first and second jib parts being contractable by said screw member to a combined length which is shorter than the height of said crane post so as to be foldable downwardly to an inoperative position in front of said crane post and substantially parallel thereto, said crane post being hollow and having an open front, said hydraulic jack means being connected hingedly to said crane post and to said first jib part so as to be received in said hollow crane post through said open front of the latter when said jib is in said downwardly folded, inoperative position.

2. In a portable crane, the combination of a rotary hollow crane post having an open front, a jib consisting of first and second parts telescopically movable relative to each other so as to be extensible from a contracted condition in which the length of said jib is less than the height of said post, a load attachment device at the free end of said second jib part, first hinge means connecting the top of said crane post with the end of said first jib part remote from said second jib part for vertical swinging of the jib relative to the crane post, said first hinge means extending laterally across the crane post and being spaced downwardly from said jib when the latter is in raised operative positions so that said end of the jib is fully exposed in all positions of the jib and the latter is foldable downwardly, when in said contracted condition, to an inoperative position in front of said crane post and substantially parallel thereto, hydraulic jack means pivotally connected, at its lower end, within the lower end of said hollow crane post and being extensible through said open front of said post, and second hinge means connecting the upper end of said jack means with said first jib part and being also spaced downwardly from the latter in said raised operative positions thereof so that said hydraulic jack means is substantially entirely housed in said hollow crane post when said jib is in said inoperative position.

3. A portable crane according to claim 2; further comprising means operable from said exposed end of the first jib part to effect telescopic movement of said second 11b part relative to said first jib part.

4. A portable crane according to claim 2; wherein sald hydraulic jack means includes, as a self-contained unit, a cylinder and a ram extending therefrom, an oil reservoir, an oil pump operable to pump oil from said reservoir into said cylinder for raising said jib from said inoperative position, a selectively operable oil return valve for controlling the return of oil from said cylinder to said reservoir, and check valve means by-passing said pump to permit quick raising of said jib from its inoperative position by manual actuation of the jib.

5. A portable crane according to claim 2; wherein said hydraulic jack means includes, as a self-contained unit, a cylinder and a ram extending therefrom, an oil reservoir, an oil pump operable to pump oil from said reservoir into said cylinder for raising said jib from said inoperative position and a selectively operable oil return valve for controlling the return of oil from said cylinder to said reservoir; and wherein said crane post has a conical swivel pin projecting from its lower end, said swivel pin being adapted to be removably received in a socket secured in a base at the site where the crane is to be used and forming the only connection between the post and base, so that the crane may be easily removed from the base without disconnection of any of the components of said hydraulic jack means.

References Cited UNITED STATES PATENTS 2,862,628 12/1958 Coates et al. 212- 3,109,541 11/1963 Matson 2l2-65 FOREIGN PATENTS 187,912 11/1922 Great Britain.

ANDRES H. NIELSEN, Primary Examiner, 

1. IN A SMALL SIZE CRANE COMPRISING A ROTARY CRANE POST, A VERTICALLY SWINGABLE, EXTENSIBLE JIB MOUNTED ON THE CRANE POST, AND HYDRAULIC JACK MEANS TO EFFECT VERTICAL SWINGING MOVEMENT OF THE JIB; SAID EXTENSIBLE JIB CONSISTING OF A FIRST JIB PART AND A SECOND JIB PART TELESCOPICALLY MOVABLE RELATIVE TO SAID FIRST JIB PART AND HAVING A FIXED LOAD ATTACHMENT DEVICE AT ITS OUTER FREE END, HINGE MEANS LATERALLY OUTSIDE SAID FIRST CONNECTING THE END OF THE LATTER REMOTE FROM SAID SECOND JIB PART TO THE TOP OF SAID CRANE POST SO THAT SAID END OF THE FIRST JIB PART REMAINS FULL EXPOSED IN ALL POSITIONS OF THE JIB, SAID TELESCOPICALLY MOVABLE FIRST AND SECOND JIB PARTS BEING INTERCONNECTED BY A SCREW MEMBER EXTENDING LONGITUDINALLY THROUGH SAID FIRST JIB PART AND INTO SAID SECOND JIB PART, MEANS ROTATABLY JOURNALLING SAID SCREW MEMBER IN SAID FIRST JIB PART TO PREVENT RELATIVE AXIAL MOVEMENT THEREOF, MEANS FIXED IN SAID SECOND JIB PART DEFINING COOPERATING THREADS ENGAGING SAID SCREW MEMBER TO MOVE SAID SECOND JIB PART IN CONTROLLED MANNER RELATIVE TO SAID FIRST JIB PART UPON ROTATION OF SAID SCREW MEMBER, AN END OF SAID SCREW MEMBER REMOTE FROM SAID SECOND JIB PART PROJECTING FROM SAID EXPOSED END OF THE FIRST JIB PART AND CONSTITUTING A COUPLING MEMBER WHICH IS READITY ACCESSIBLE FOR TURNING BY A SCREWTURNING TOOL, SAID FIRST AND SECOND JIB PARTS BEING CONTRACTABLE BY SAID SCREW MEMBER TO A COMBINED LENGTH WHICH IS SHORTER THAN THE HEIGHT OF SAID CRANE POST SO AS TO BE FOLDABLE DOWNWARDLY TO AN INOPERATIVE POSITION IN FRONT OF SAID CRANE POST AND SUBSTANTIALLY PARALLEL THERETO, SAID CRANE POST BEING HOLLOW AND HAVING AN OPEN FRONT, SAID HYDRAULIC JACK MEANS BEING CONNECTED HINGEDLY TO SAID CRANE POST AND TO SAID FIRST JIB PART SO AS TO BE RECEIVED IN SAID HOLLOW CRANE POST THROUGH SAID OPEN FRONT OF THE LATTER WHEN SAID JIB IS IN SAID DOWNWARDLY FOLDED, INOPERATIVE POSITION. 